class Solution {
public:
    vector<vector<int>> fourSum(vector<int>& nums, int target) {
        sort(nums.begin(), nums.end());
        vector<vector<int>> ret;

        for (int i = 0; i < nums.size();) {
            for (int j = i + 1; j < nums.size();) {
                long long aim = (long long)target - nums[i] - nums[j];
                int left = j + 1, right = nums.size() - 1;

                while (left < right) {
                    if (nums[left] + nums[right] < aim)  left++;
                    else if (nums[left] + nums[right] > aim)   right--;
                    else
                    {
                        ret.push_back({ nums[i],nums[j],nums[left],nums[right] });
                        left++;
                        right--;
                        while (left < right && nums[left] == nums[left - 1]) left++;
                        while (left < right && nums[right] == nums[right + 1])   right;
                    }
                }
                j++;
                while (j < nums.size() && nums[j] == nums[j - 1]) j++;
            }
            i++;
            while (i < nums.size() && nums[i] == nums[i - 1]) i++;
        }

        return ret;
    }
};